ABSTRACT Acute otitis media (AOM) is by far the most frequent indication for antibiotic prescription in young children (~10 million prescriptions per year). Even though antibiotics are given largely to reduce symptoms of AOM, until recently no outcome measures had been developed to track improvement or deterioration of symptoms in trials assessing the efficacy of antibiotics. As a direct result of the unavailability of such a measure, little data are available on the impact of various treatments on resolution of symptoms. Accordingly, clinicians currently have to choose an antibiotic for a patient without knowing if it is superior to other available treatment options at reducing the severity of symptoms of AOM. We previously developed a parent-reported outcome measure to track the severity of symptoms of AOM in preverbal children. Although we have successfully used this outcome measure?the Acute Otitis Media Severity of Symptoms Scale (AOM-SOS)?in a number of recent trials, our approach in developing the measure had important shortcomings, of which the most notable was the lack of extensive qualitative research to establish concepts and items to include in the measure. Accordingly, the objectives of the proposed research are (a) to perform the necessary qualitative work to allow us to modify the AOM-SOS so that it comprehensively captures all factors relevant to parents, and (b) to assess the psychometric properties of the modified scale. To achieve these objectives we will (1) conduct in-depth, semi- structured interviews with parents of children with AOM, (2) analyze transcripts using best available qualitative research methods, (3) reduce the number of items using established methods, (4) develop a pilot version of the outcome measure from this reduced list of items, (5) use rounds of cognitive interviews to refine the measure, (6) translate the measure into Spanish and ensure comparability through cognitive interviews with Spanish-speaking parents, and (7) assess the reliability, construct validity, and responsiveness of the modified measure. The work outlined here will allow us to submit a qualification-ready version of the AOM-SOS to the FDA by the end of the project period. Absent a study of this nature, investigators will continue to rely on surrogate outcomes with questionable clinical relevance in their trials and clinicians will continue to prescribe treatments without knowing if they improve the symptoms of their patients.